The effects of antiseptics on dental plaque samples obtained from monkeys has been evaluated using conventional microbiologic as well as adenine nucleotide analysis. Consistent interpretations of the data were obtained from both methods. The persistent effects previously noted for Octenidine have been tested for significance statistically and confirmed. Plaque fluids obtained from monkeys before and after application of sucrose have been analysed for their volatile metabolic products using high resolution capillary column and a gas chromatograph. A variety of volatile fatty acids were demonstrated in the plaque fluid samples and a decrease in the proportions of acetic and propionic to butyric acids was demonstrated.